You'd be better off saving the money and buying a starter. A new engine won't solve your problem. A starter almost definately will!

How new is the engine? Newer engines seem to be harder to hand start to me. There is also a bit of a knack to it. If you have some nearby with a starter, try and borrow it (and them) to get the engine started. Then you can adjust the needle. Once this is done try hand starting it again and see how you go.